Reading Comprehension VIP Practice Exam

PASSAGE 1 — Read the following passage and answer Questions 1–5. The human gut harbors approximately 100 trillion microorganisms, collectively known as the gut microbiome. These microorganisms — including bacteria, viruses, fungi, and archaea — outnumber human cells by a ratio of roughly 1.3 to 1. Far from being mere passengers, gut microbes play essential roles in digestion, immune regulation, and even mental health. The gut-brain axis, a bidirectional communication network linking the enteric nervous system with the central nervous system, is now understood to transmit signals that influence mood, cognition, and behavior. Studies have demonstrated that germ-free mice — raised in sterile conditions without gut microbiota — exhibit heightened anxiety-like behaviors and altered stress responses compared to conventionally raised mice, suggesting that microbial colonization shapes neurological development. Moreover, disruptions in microbiome composition, termed dysbiosis, have been associated with conditions ranging from inflammatory bowel disease to autism spectrum disorder, though the causal mechanisms remain incompletely understood. What is the primary purpose of this passage?

Questions 2–30 and full explanations are VIP-exclusive.